1961 Philips CSX 900W

The xenon short-arc lamp shown here features a very early design and was in fact manufactured by Osram in West Berlin, FRG. Since the latter essentially developed the technology into commercial products, it acquired a crucial experience in this domain, which placed them in a prominent place in all markets targeted by this type of lamp (primarily cinema projection and instrument illumination). The manufacturing of xenon short-arc lamps is very specialized and requires highly trained glass blowers to make and assemble its many parts. Because this production process could not be easily set up, Philips (the Netherlands) resorted to outsource its CSX to Osram when it started listing these lamps in the second half of the 1950s. The Dutch eventually began making their own xenon lamps in Eindhoven, the Netherlands, in the early 1970s.

The present CSX 900W has an interesting construction which includes asymetrical electrodes for an operation on DC power. The anode is the largest electrode since it must dissipate the energy of free electrons collected from the hot arc plasma. Characteristic of early xenon arc lamps, the CSX 900W is designed for a vertical operation with the anode in the top position, which enables a stable arc operation thanks to the smooth channeling of the strong gas flow driven by convection and electro-kinetic forces present at the cathode tip (i.e., Maecker effect). The massive anode also has a tip profile designed for the smooth deflection of the upward gas flow. Both electrodes are held into place by two sections of the quartz bulb which are collapsed onto the supporting rods, which also limits the forces applied to the fragile graded-glass feedthroughs located at each extremity of the lamp.

This arc lamp technology still remains the workhorse of cinema projection lighting today due to its unparallel arc luminance, color quality and stability over service life. Remarkably, most of its design features have hardly changed since the origin, which is a testament of the quality of early developments in the 1940s and 50s which left little room for further improvements. Changes in the 1970s include an operation in the horizontal position, first with the help of magnetic arc stabilization and then with the shortening of the arc. The anode was also redesigned with a front face and a larger surface area in order to better dissipate energy.